Recently, electronic components are becoming higher in performance and the packing density of electronic components on a control board is becoming higher, and the amount of heat generation from the control board is increasing dramatically. As a result, the internal temperature of the heating element storing box for accommodating electronic components tends to be higher, and the temperature in the heating element storing box has a vital effect on guarantee of operation and product life of electronic components mounted on the control board. It is hence demanded to cool the temperature in the heating element storing box below a specific point by using a cooling device.
Conventionally, this kind of cooling device is known to include a heat transfer plate as a sensible heat exchanger, an indoor air suction fan as an indoor air blower, an outdoor air suction fan as an outdoor air blower, and terminal blocks. Such conventional cooling device is disclosed, for example, in patent document 1 (Japanese Utility Model Application Laid-Open No. H5-8253).
The conventional cooling device is described below while referring to FIG. 16. Cooling device 101 is provided inside of door 102 of control panel 100 as a heating element storing box, and is separated into control panel inner space 103 (hereinafter called space 103) and control panel outer space 104 (hereinafter called space 104). Cooling device 101 has case 105 formed like a long box, and flange 106 formed vertically and laterally for mounting cooling device 101 on door 102. The front side of flange 106 is provided with packing 107 for keeping airtight with door 102.
Case 105 includes indoor air intake hole 108 as an indoor air suction port, and indoor air exhaust hole 109 as an indoor air blow port. Heat transfer plate 110 is accommodated in the center of case 105. Heat transfer plate 110 is made of a thin plate folded in corrugated shape, and multiple barrier walls are formed at equal intervals, and both end portions in the longitudinal direction are alternately connected every one other by bridge portions, thereby forming a plurality of indoor air side square passages 111 (hereinafter called passages 111) and outdoor air side square passages 112 (hereinafter called passages 112) positioned alternately. Indoor air intake hole 108 communicates with passages 111. Indoor air exhaust hole 109 is provided with indoor air suction fan 113 (hereinafter called fan 113) as an indoor air blower by way of mounting plate 114. The upper edge of mounting plate 114 has slope 114A for deflecting the flow of indoor air.
In the middle of door 102, outdoor air intake hole 115 is provided as an outdoor air suction port, and outdoor air exhaust hole 116 as an outdoor air blow port is formed in the upper part of door 102. Outdoor air intake hole 115 communicates with passages 112. Outdoor air exhaust hole 116 is provided with outdoor air suction fan 117 (hereinafter called fan 117) as an outdoor air blower by way of mounting plate 118.
Terminal blocks 119 are provided in the upper part of case 105 and in the upper part of mounting plate 114. Lead wire 113A of fan 113 and lead wire 117A of fan 117 are respectively connected to the inside of terminal blocks 119, and are connected outside of case 105 by using wires 120. Wires (not shown) are distributed from either one of two terminal blocks 119.
When cooling device 101 is put in operation, the high temperature air in space 103 is sucked in from indoor air intake hole 108 as indicated by arrow a, and is distributed in passages 111, and is returned again into space 103 by means of fan 113. On the other hand, the low temperature air in space 104 is sucked in from outdoor air intake hole 115 as indicated by arrow b, and is distributed in passages 112, and is returned again into space 104 by means of fan 117. By such forced convection, heat is exchanged through barrier walls of heat transfer plate 110, and the air in control panel 100 is cooled.
Recently, in order to operate cooling device 100 more efficiently, it has been attempted to develop cooling device 100 having a control device (not shown) for controlling the operation of fan 113 and the operation of fan 117. In such conventional cooling device 100, however, the control device is installed in a section in which fan 113 or fan 117 is disposed. Therefore, depending on the location of the control device, the air flow rate may be lowered, or the air blowing state to the heat transfer plate may be biased, and the cooling capacity may tend to decline.    Patent document 1: Japanese Utility Model Application Laid-Open No. H5-8253